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Like other organisms, the plants are continually exposed in their environment to a wide range of different stresses, originated from human activities (air pollutants, acid rain, xenobiotics) or having natural causes such as drought, low or high temperature, high light intensities and nutrient deficiency. A common feature of various biotic and abiotic stress factors is their potential to increase the production of reactive oxygen species (ROS) in plant tissues. ROS are also generated in plant cells during normal metabolic functions. Free radicals are highly reactive chemically and can induce extensive degradation of membrane lipids, proteins and DNA. The ability of a plant to reduce the harmful effects of free radical determines its tolerance to such a stress. To prevent such damages the plants have developed antioxidative system composed of non-enzymic antioxidants such as glutathione, vitamin C (ascorbate) and E (α-tocopherol) as well as protective enzymes (e.g. superoxide dismutase, ascorbate peroxidase, glutathione reductase ). The problem of yield decrease in crop species grown und er stress conditions has focused the attention on metabolic mechanisms and substances differentiating plant susceptibility to injuries caused by various environmental stresses.
This study was to discover if there is any relationship between antioxidant status after harvest and bioactives fate during apple storage. The clearer link in this issue concerned enzymatic part of antioxidant apparatus, for which the particularly high year effect was noted. Except for anthocyanins, non-enzymatic bioactives end-status was not strictly related to their harvest size. However the content during the first months of storage might be closely connected with antioxidant status measured after harvest. A significantly higher concentration of majority assessed antioxidants was characterized by apple harvested and stored in 2005/2006 season, on the average. Simultaneously many, statistically proved, correlations over storage between the examined antioxidants at that time existed. Total antioxidant power (FRAP assay) significantly increased after the first storage period, probably as a result of fruit acclimatory response to storage conditions, and next decreased. In general, changes of FRAP value reflected fluctuations of individual compounds measured in this study.
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